1. Field of the Invention
The present invention relates to a method of manufacturing a surface acoustic wave device which is applied to antenna duplexers, etc. suitable for use in cell phones, etc.
2. Description of the Related Art
A conventional surface acoustic wave device and a manufacturing method thereof will be described with reference to the accompanying drawings wherein FIG. 43 is a plan view showing a comb-like electrode and a reflector of a conventional surface acoustic wave device, FIG. 44 is a sectional view of essential parts of the conventional surface acoustic wave device, FIG. 45 is a sectional view of essential parts showing a first step of a method of manufacturing the conventional surface acoustic wave device, FIG. 46 is a sectional view of essential parts showing a second step of the method of manufacturing the conventional surface acoustic wave device, FIG. 47 is a sectional view of essential parts showing a third step of the method of manufacturing the conventional surface acoustic wave device, and FIG. 48 is a plan view showing the third step of the method of manufacturing the conventional surface acoustic wave device.
FIG. 49 is a sectional view of essential parts showing a fourth step of the method of manufacturing the conventional surface acoustic wave device, FIG. 50 is a sectional view of essential parts showing a fifth step of the method of manufacturing the conventional surface acoustic wave device, FIG. 51 is a sectional view of essential parts showing a sixth step of the method of manufacturing the conventional surface acoustic wave device, FIG. 52 is a plan view showing the sixth step of the method of manufacturing the conventional surface acoustic wave device, FIG. 53 is a sectional view of essential parts showing a seventh step of the method of manufacturing the conventional surface acoustic wave device, FIG. 54 is a plan view showing the seventh step of the method of manufacturing the conventional surface acoustic wave device, FIG. 55 is a sectional view of essential parts showing an eighth step of the method of manufacturing the conventional surface acoustic wave device, FIG. 56 is a sectional view of essential parts showing a ninth step of the method of manufacturing the conventional surface acoustic wave device; and FIG. 57 is a sectional view of essential parts showing the ninth step of the method of manufacturing the conventional surface acoustic wave device.
Next, the construction of a conventional surface acoustic wave device will be described with reference to FIGS. 43 and 44. Referring to these drawings, on one surface of a piezoelectric substrate 51 is formed a conventional surface acoustic wave device including a paired set of two inter digital transducer 52a and 52b, electrode sections 53a and 53b connected to the inter digital transducer 52a and 52b, respectively, a conductor layer 55 formed on the electrode sections 53a and 53b, with an intermediate layer 54 made of a metal different from the electrode sections 53a and 53b between the conductor layer and the electrode sections, bumps 56 formed on portions of the conductor layer 55, ladder-like reflectors 57a and 57b provided adjacent to both sides of the inter digital transducer 52a and 52b, and an insulating film 58 provided so as to cover an entire region of the inter digital transducer 52a and 52b and the reflectors 57a and 57b 
Next, a method of manufacturing the conventional surface acoustic wave device having such a construction will be described with reference to FIGS. 45 to 57. First, a negative resist film 60 is formed on the one entire surface of the piezoelectric substrate 51 and then exposed using a mask. Thereafter, the exposed resist film 60, as shown in FIG. 45, is left by removing the resist film 60, which has not been exposed, by a solution.
That is, the resist film 60 is disposed in clearances (spots where a conductor is not formed) between the inter digital transducer 52a and 52b and the reflectors 57a and 57b. 
Next, as shown in FIG. 46, a conductor is formed on the one entire surface of the piezoelectric substrate 51 by vapor-depositing a conductive material. Thereafter, as shown in FIGS. 47 and 48, when the resist film 60 is removed, inter digital transducer 52a and 52b, electrode sections 53a and 53b, reflectors 57a and 57b, and a protective conductor 61 which electrically connects the electrodes, the electrode sections, and the reflectors with one another, are formed.
Next, a negative resist film 60 is formed on one entire surface of FIGS. 47 and 48, and exposed with the electrode sections 53a and 53b being masked. Thereafter, as shown in FIG. 49, the exposed resist film 60 is left on the electrode sections 53a and 53b by removing the resist film 60 on the electrode sections 53a and 53b, which has not been exposed, by a solution.
Next, as shown in FIG. 50, a conductive material is vapor-deposited on one entire surface of the piezoelectric substrate 51, thereby forming a conductor composed of an intermediate layer 54 and a conductor layer 55. Thereafter, as shown in FIGS. 51 and 52, when the resist film 60 is removed, a conductor layer 55 is formed on the electrode sections 53a and 53b, with an intermediate layer 54 therebetween.
Next, as shown in FIGS. 53 and 54, bumps 56 are formed on portions of the conductor layer 55. Thereafter, as shown in FIG. 55, an insulating film 58 is formed on sputtering. After that, as shown in FIG. 56, the portion of the insulating film 58 excluding the regions of the inter digital transducer 52a and 52b and reflectors 57a and 57b are removed.
Next, as shown in FIG. 57, the inter digital transducer 52a and 52b having the electrode sections 53a and 53b, and the reflectors 57a and 57b are independently formed by removing the protective conductor 61 by etching. Thereafter, as shown in FIG. 44, when an adjustment of thinning the insulating film 58 is made so that the surface acoustic wave device has a desired frequency characteristic, manufacture of the conventional surface acoustic wave device is completed.
In the method of manufacturing the conventional surface acoustic wave device, the inter digital transducer 52a and 52b, the reflectors 57a and 57b, and the protective conductor 61 which electrically connects the electrodes and the reflectors with one another are formed on one surface of the piezoelectric substrate 51. Thereafter, the conductive layer 55 is formed on the electrode sections 53a and 53b with the intermediate layer 54 therebetween, and the bumps 56 are formed on the conductor layer 55. After the step, the regions of the inter digital transducer 52a and 52b and reflectors 57a and 57b are covered with the insulating film 58. Therefore, there is a problem in that, in the processes before the insulating film 58 is formed, foreign matters may stick to the regions of the inter digital transducer 52a and 52b and reflectors 57a and 57b, thereby worsening the performance.
Further, since the formation regions of the intermediate layer 54 and conductor layer 55 are formed by the resist film 60 when the intermediate layer 54 and the conductor 55 are formed, there is a problem in that the number of manufacturing processing increases, thus resulting in a high cost.